import java.util.Scanner;

public class demo02 {
    //养兔子
    public static void main(String[] args) {
        long[] arr=new long[91];
        arr[0]=1;
        arr[1]=1;
        for (int i = 2; i <= 90; i++) {
            arr[i]=arr[i-1]+arr[i-2];
        }
        Scanner sc=new Scanner(System.in);
        while (sc.hasNext()){
            int n=sc.nextInt();
            System.out.println(arr[n]);
        }
    }
}
